this slide is for skin layers and its histological view with labelled diagrams................Best regards my Teachers Histology of Skin, integument histology, integument, Ali Asadullah Studento of DVM

1. The Integumentary System-2
Ali Asadullah

2. Learning outcomes
 Keratinocytes and non-keratinocytes
 Layers of Dermis
 Hypodermis
 Thick and thin skin
 Appendages

3. Tactile epithelioid cells, also known as Merkel cells, are located in
the basal region of the epidermis in both hairless and hairy skin.
Its nucleus is lobulated and irregular, and the cytoplasm is clear .

4.  Tactile epithelioid cells are connected to adjacent
keratinocytes by desmosomes.
 When associated with an axon, a tactile epithelioid
cell–neurite complex or non-encapsulated tactile
corpuscle is formed.
 Specialized areas of skin containing these complexes
are known as tactile hair discs.
 Tactile epithelioid cells can also stimulate
keratinocyte growth.
 In addition, tactile epithelioid cells can function as
receptors for touch.

5.  The dendritic cells located in the epidermis
are called intraepidermal macrophages
(Langerhans cells).
 Intraepidermal macrophages are most
commonly found in the upper spinous layer
of the epidermis.
 Reported in adult pigs, cats, dogs, human
and rodents.

6. Langerhans cells
 Also identified in the stratified
squamous epithelium of the upper
digestive tract, female genital tract and
sheep rumen.

7. Langerhan cell (cont..
 At the ultrastructural level, intraepidermal macrophages have a
depressed nucleus and the cytoplasm contains typical organelles.
 A unique feature of this cell is distinctive rod- or racket-shaped
granules in the cytoplasm that are known as intraepidermal
macrophage (Birbeck) granules.
 Langerhans cells are capable of presenting antigen to lymphocytes
.

9. Dermis
 Strong, flexible connective tissue
 Cells: fibroblasts, macrophages, mast cells, WBCs
 Fiber types: collagen, elastic, reticular
 Rich supply of nerves and vessels
 Critical role in temperature regulation (the vessels)
 Two layers (see next slides)
 Papillary – areolar connective tissue; includes dermal
papillae
 Reticular – “reticulum” (network) of collagen and reticular
fibers

10. Layers of the dermis
Papillary layer
Reticular layer

11. *Dermis layers
*
*
*Dermal papillae

12. thin skin thick skin
Thin (hairy) skin vs Thick (hairless) skin

13. Epidermis and dermis of (a) thick skin and (b) thin skin
(which one makes the difference?)

14. Hypodermis
 “Hypodermis” (Gk) = below the skin
 “Subcutaneous” (Latin) = below the skin
 Also called “superficial fascia”
“fascia” (Latin) =band;
in anatomy: sheet of connective tissue
 Fatty tissue which stores fat and anchors skin (areolar
tissue and adipose cells)

15. Skin appendages
 Derived from epidermis but extend into dermis
 Include
Hair and hair follicles
Sebaceous (oil) glands
Sweat (sudoriferous) glands
Nails

16. Nails
 Of hard keratin
 Corresponds to hooves and claws
 Grows from nail matrix

17. Hair and hair follicles: complex
Derived from epidermis
Everywhere but palms, soles, nipples, parts of genitalia
*“arrector pili” is smooth muscle
*
Hair papilla
is connective
tissue________________
Hair bulb:
epithelial cells
surrounding
papilla

18.  Functions of hair
 Warmth – less in man than other mammals
 Sense light touch of the skin
 Protection - scalp
 Parts
 Root imbedded in skin
 Shaft projecting above skin surface
 Make up of hair – hard keratin
 Three concentric layers
 Medulla (core)
 Cortex (surrounds medulla)
 Cuticle (single layers, overlapping)

19.  Hair color
Amount of melanin for black or brown; distinct
form of melanin for red
White: decreased melanin and increase air bubbles
in the medulla

20. Epidermal Appendages
Hair follicle
Apocrine
Sweat gland
Eccrine
Sweat gland
Sebaceous gland
Arrector pili
muscle
*also nails and
mammary glands

21. Hair Follicles

22. Arrector Pili Muscle

23. Hair Follicles

24. Sebaceous (oil) glands
 Entire body except palms and soles
 Produce sebum by holocrine secretion
 Oils and lubricates

25. Epidermal Appendages
Hair follicle
Apocrine
Sweat gland
Eccrine
Sweat gland
Sebaceous gland
Arrector pili
muscle
*also nails and
mammary glands

26. Sebaceous glands
sebocytes secrete sebum: triglycerides,
fatty acids, waxes

27. Sebaceous gland

28. Sweat glands
 Entire skin surface
except nipples and
part of external
genitalia
 Prevent
overheating
 Produced in
response to stress
as well as heat

29. Types of sweat glands
 Eccrine or merocrine
 Most numerous
 True sweat: 99% water, some salts, traces of waste
 Open through pores
 Apocrine
 Axillary, anal and genital areas only
 Ducts open into hair follicles
 The organic molecules in it decompose with time - odor
 Modified apocrine glands
 Ceruminous – secrete earwax
 Mammary – secrete milk

30. Epidermal Appendages
Hair follicle
Apocrine
Sweat gland
Eccrine
Sweat gland
Sebaceous gland
Arrector pili
muscle
*also nails and
mammary glands

31. Apocrine Sweat Glands
secrete a mixture of carbs, lipids,
protein and ammonia

32. Apocrine Sweat Glands
simple cuboidal or
columnar
secretory cells and
myoepithelial cells

33. Epidermal Appendages
Hair follicle
Apocrine
Sweat gland
Eccrine
Sweat gland
Sebaceous gland
Arrector pili
muscle
*also nails and
mammary glands

34. Eccrine Sweat Glands

36.  The mammary gland is a
compound- tubuloalveolar
gland.
 The secretory units form
lobules separated by
connective-tissue septa.
Mammary Gland

37. Alveoli
 Secretory alveoli of the mammary gland
are spherical to ovoid in shape with a
large lumen.
 Adjacent alveoli may fuse partially.
 The lumen is partially collapsed and
irregular in outline.
 Clusters of alveoli form lobules within
the gland.

39. Alveoli
 The epithelium of the alveoli varies markedly in height
during various stages of secretory activity.
 During active secretion, the basal portion of the
columnar epithelial cells contains a well-developed
rough endoplasmic reticulum.
 At the end of the secretory cycle, the epithelial cells are
low cuboidal in shape.

40. Interstitium
 The interstitial tissue of the mammary gland provides
important structural support for the secretory units and
contains the blood vessels, lymph vessels, and nerves.
 Each secretory unit is surrounded by loose connective
tissue with an extensive plexus of blood and lymph
capillaries.
 The interlobular connective tissue is thick and contains the
interlobular ducts and larger blood and lymph vessels.

41. Ducts
 The duct system begins with an intralobular duct
which drains into an interlobular duct.
 The interlobular duct, in turn, drains into a
lactiferous duct, which is the primary excretory duct
for a lobe.
 The intralobular duct epithelium is simple cuboidal.
 Spindle-shaped myoepithelial cells may be associated
with these ducts.

43. Teat
 The teat, or nipple, contains the terminal part of the duct system.
 The lactiferous sinus is continuous with the teat sinus (teat cistern, cavity
of the teat), which is lined by stratified cuboidal epithelium.
 The teat sinus empties into one or more papillary ducts (teat canal, streak
canal) leading to the external surface of the teat.
 A single papillary duct is present in ruminants while multiple papillary
ducts open separately onto the teat surface of other species.
 Horses have 2 papillary ducts, pigs have 2 to 3, cats have
4 to 7, and dogs have 7 to 16.
 The papillary duct is lined with stratified squamous epithelium.

44. Teat
 The skin of the teat in cows and sows is composed
of a thick, keratinized stratified squamous
epithelium and dermis without hair follicles and
sweat or sebaceous glands.
 However, in some domestic species, such as sheep
and goats, the teat may contain fine hairs and sweat
and sebaceous glands.

45. Hypodermis

46. Hypodermis
Dermis
Hypodermis

47. Major Points
 The dermis is a dense irregular connective tissue with dermal
papillae that contain capillaries
 Many types of nerve endings are found in different parts of
the skin
 Epidermal appendages are derived from the epidermis and
include hair follicles, apocrine sweat glands, eccrine sweat
glands, and sebaceous glands
 The hypodermis is a fatty connective tissue layer that
surrounds some epidermal appendages